Experimental densities of subcooled deuterium oxide at pressures up to 160 MPa

In this work, the experimental results of deuterium oxide density at high pressure and in a wide range of temperatures, by means of the pseudo-isochoric method, are presented. A specific stainless steel cell was devised to be used as a pycnometer and filled with variable mass of heavy water. The latter was measured by weighing with an analytical balance and using the substitution method. The volume of the pycnometric cell was measured by the gravimetric method and corrected for the effect of temperature and pressure. Each measurement cycle was performed at constant mass, measuring pressure as a function of temperature at equilibrium. From the mass and volume values, density was calculated according to its definition. Heavy water density was measured for temperatures down to 253 K and for pressures up to 163 MPa, thus both in stable and supercooled metastable states. All terms contributing to the uncertainty in determining the volume and the mass were considered, obtaining an expanded relative uncertainty of deuterium oxide density of 0.04%.